1. Technical Field of the Invention
The present invention relates to a power transmission system for a hybrid vehicle having a motor/generator and torque converter disposed in series between a crankshaft of an engine and a main shaft of a transmission.
2. Related Art
A conventional hybrid vehicle is disclosed by Japanese Patent Application Laid-open No. 2000-85387 in which a motor/generator and a torque converter are connected in series between a crankshaft of an engine and a main shaft of a transmission. The motor/generator functions as a generator allowing a battery to be charged or energy to be recovered by regenerative braking. The motor/generator also functions as a motor allowing the engine to be started or the output of the engine to be assisted.
However, in the above-described conventional hybrid vehicle, because a side cover of the torque converter and a rotor of the motor/generator face each other via a small gap, radiant heat from the torque converter, which has an increased temperature due to its operation, is transferred to the rotor via the small gap. Therefore, there is a drawback in that the temperature of the motor/generator increases, which deteriorates overall motor/generator performance. Furthermore, because the inner peripheral section of the side cover and the inner peripheral section of the rotor are connected via a boss, the heat of the torque converter is transferred from the side cover to the rotor via the boss, which also increases the temperature of the motor/generator and adds to the overall deterioration of motor/generator performance.
It is an object of the present invention to at least overcome the above-described drawbacks. It is also an object of the present invention to minimize heat transfer from a torque converter to a motor/generator when the motor/generator and the torque converter are disposed between an engine and a transmission.
In order to achieve the above-mentioned objects, in accordance with a first aspect of the present invention, there is provided a power transmission system for a hybrid vehicle having a motor/generator and a torque converter. The motor/generator and the torque converter are disposed in series between a crankshaft of an engine and a main shaft of a transmission. An inner peripheral section of a drive plate extending radially inward from an outer peripheral section of the torque converter is connected to a rotor of the motor/generator.
In accordance with the above-described arrangement, since the inner peripheral section of the drive plate extending radially inward from the outer peripheral section of the torque converter is connected to the rotor of the motor/generator, the radiant heat radiated from the torque converter having an increased temperature is shielded by the drive plate. Accordingly, it is difficult for the heat to reach the motor/generator, which suppresses any degradation in motor/generator performance that typically accompanies an increase in the temperature of the motor/generator. Because the sheet-shaped drive plate is very effective in dissipating heat, the amount of heat transferred from the torque converter to the rotor of the motor/generator via the drive plate is reduced, thereby further effectively preventing any increase in the temperature of the motor/generator.
In accordance with a second aspect of the present invention, in addition to the first aspect, there is provided a power transmission system for a hybrid vehicle wherein a boss projects radially outward from the outer peripheral section of the torque converter, and an outer peripheral section of the drive plate is connected to the boss.
In accordance with the above-described arrangement, connecting the outer peripheral section of the drive plate to the boss projecting radially outward from the outer peripheral section of the torque converter makes it difficult for the heat of the torque converter to be directly transferred to the drive plate, thereby further effectively preventing any increase in the temperature of the motor/generator.
In accordance with a third aspect of the present invention, in addition to the first aspect, there is provided a power transmission system for a hybrid vehicle wherein a gap is disposed in the vicinity of the region where the drive plate is connected to the outer peripheral section of the torque converter.
In accordance with the above-described arrangement, because the gap is provided in the vicinity of the region where the drive plate is connected to the outer peripheral section of the torque converter, the amount of heat transferred from the torque converter to the motor/generator via the drive plate is further reduced.
Furthermore, in accordance with a fourth aspect of the present invention, in addition to the first aspect, there is provided a power transmission system for a hybrid vehicle wherein a gap is disposed in the vicinity of the region where the inner peripheral section of the drive plate is connected to the rotor of the motor/generator.
In accordance with this arrangement, because the gap is provided in the vicinity of the region where the inner peripheral section of the drive plate is connected to the rotor of the motor/generator, the amount of heat transferred from the torque converter to the motor/generator via the drive plate is further reduced.
Moreover, in accordance with a fifth aspect of the present invention, in addition to the first aspect, there is provided a power transmission system for a hybrid vehicle wherein a support hole supporting a shaft end of the output shaft of the torque converter is disposed in the center of the rotor of the motor/generator.
In accordance with this arrangement, because the shaft end of the output shaft of the torque converter is supported in the support hole disposed in the center of the rotor of the motor/generator, the axis of the motor/generator can be made to coincide with the axis of the torque converter while minimizing any increase in the heat conducting area through which heat is transferred from the torque converter to the motor/generator.
A main shaft forms the output shaft of the torque converter of the present invention.